Electric generation from renewable energy resources, such as wind and solar farms, is intermittent and unpredictable. The electric grid is designed to connect to available and predictable power plants and is negatively affected by intermittent generation.
The typical 12 kV electric distribution circuit is capable of accepting < or =1 MW of electric generation without infrastructure improvements and with minimal impact on electric system voltage and frequency. Connecting medium-scale (>1 MW) electric power plants to the electric distribution system or electric transmission system risks grid stability. For example, a 14 MW solar power plant located in Arizona is causing fluctuations in system frequency and voltage when clouds pass over the site. This has caused numerous problems with the connected utility grid.
More generally, if the output of a renewable energy power plant is greater than 10% of the line capacity, temporary unavailability can adversely affect power grid stability. As a result, current renewable energy power plants that are operated independently supply only a small percentage of line capacity and do not provide a significant portion of power consumed by a utility company's customers.
Accordingly, in light of these difficulties, there exists a need for a distributed hybrid renewable energy power plant.